Generation of higher harmonics of monochromatic electromagnetic radiation

Various methods and systems are provided for generation of higher harmonics of monochromatic electromagnetic radiation. In one embodiment, among others, a system includes a double array of planar structures including a first periodically structured planar structure having a periodic spacing corresponding to a resonant frequency and a second periodically structured planar structure in parallel with the first structure. The system also includes a source configured to illuminate the first structure with a beam of monochromatic electromagnetic radiation at the resonant frequency to produce a higher harmonic of the monochromatic electromagnetic radiation. In another embodiment, a method includes directing a beam of monochromatic electromagnetic radiation at a resonant frequency at a double array of planar structures and generating a higher harmonic of the monochromatic electromagnetic radiation. The double array includes a first periodically structured planar structure and a second periodically structured planar structure in parallel with the first structure.